Science News - Cassini mission to Saturnhttps://www.sciencenews.org/editors-picks/cassini-mission-saturn?mode=pick&context=2770
enThese are Cassini’s parting shots of the Saturn systemhttps://www.sciencenews.org/blog/science-ticker/these-are-cassinis-parting-shots-saturn-system?mode=pick&context=2770
<div class="field field-name-field-op-blogpost-blog field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even">Science Ticker</div></div></div><div class="field field-name-field-op-section-term field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;tt=37" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Astronomy</a>,</div><div class="field-item odd"><a href="/search?mode=pick&amp;context=2770&amp;tt=39" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Planetary Science</a>,</div></div></div><div class="field field-name-field-topic-editor-pick-ref field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;ep=2770" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Cassini mission to Saturn</a></div></div></div><div class="field field-name-field-op-author field-type-node-reference field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:creator schema:creator"><div class="view view-openpublish-related-content view-id-openpublish_related_content view-display-id-block_1 view-dom-id-730a5de3b6c399a88c4c5fb17bfecf64">
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<span itemprop="name"><a href="/author/lisa-grossman?mode=pick&amp;context=2770">Lisa Grossman</a></span> </div>
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<div class="views-field views-field-published-at"> <span class="field-content">12:09am, September 15, 2017</span> </div> </div>
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</div></div></div></div><div class="field field-name-field-op-main-image field-type-image field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:associatedMedia schema:associatedMedia" resource="https://www.sciencenews.org/sites/default/files/2017/09/main/blogposts/091417_cassinifinalpics_main2_gring2.jpg"><img typeof="foaf:Image" src="https://www.sciencenews.org/sites/default/files/2017/09/main/blogposts/091417_cassinifinalpics_main2_gring2.jpg" width="860" height="460" alt="Saturn&#039;s G Ring" /></div></div></div><div class="field field-name-field-op-caption field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>The Cassini spacecraft took one final round of images on its farewell tour of the Saturnian system. This raw image, taken September 13 and received on Earth on September 14, showcases Saturn’s hallmark rings.</p></div></div></div><div class="field field-name-field-sn-copyright field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>JPL-Caltech/NASA, Space Science Institute</p></div></div></div><p>Here are the final images from Cassini’s last look around the Saturn system.</p><p>In its last hours before <a href="https://www.sciencenews.org/blog/science-ticker/cassini-probe-dies-tomorrow-heres-how-follow-its-end">plunging into Saturn’s atmosphere</a>, the Cassini spacecraft turned its cameras to the mission team’s favorite objects: the hydrocarbon-shrouded moon Titan, the geyser moon Enceladus and, of course, the majestic rings.</p><p>After sending these raw images back to Earth, Cassini reconfigured itself to stream data efficiently in near–real time. Image files are too big to send in this mode, so these are the last pictures Cassini will ever show us. But it will send back unprecedented information about Saturn’s atmosphere right up until the end.</p><hr /><p>The tiny moon Enceladus, which has a liquid sea below its icy surface and spews geysers of water into space, set behind Saturn as Cassini watched:</p><p><img alt="" class="caption" src="/sites/default/files/2017/09/091417_Enceladus_730x550.gif" style="width: 730px; height: 550px;" title="~~JPL-Caltech/NASA, Space Science Institute" /></p><p>Saturn looms large in this Sept. 14 raw image from the Cassini spacecraft:</p><p><img alt="" class="caption" src="/sites/default/files/2017/09/091417_cassinifinalpics_saturn_REV.jpg" style="width: 730px; height: 550px;" title="~~JPL-Caltech/NASA, Space Science Institute " /></p><p>The hazy moon Titan is the largest in the Saturn system. Its gravity nudged Cassini onto its doomed orbit when the spacecraft flew by on September 11:</p><p><img alt="" class="caption" src="/sites/default/files/2017/09/091417_cassinifinalpics_titan.jpg" style="width: 730px; height: 390px;" title="~~JPL-Caltech/NASA, Space Science Institute" /></p><span property="rnews:name schema:name" content="These are Cassini’s parting shots of the Saturn system" class="rdf-meta element-hidden"></span>Fri, 15 Sep 2017 03:50:30 +0000Helen194059 at https://www.sciencenews.orgR.I.P. Cassinihttps://www.sciencenews.org/article/rip-cassini-saturn-nasa?mode=pick&context=2770
<div class="field field-name-field-article-type field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even">News</div></div></div><div class="field field-name-field-op-section-term field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;tt=37" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Astronomy</a>,</div><div class="field-item odd"><a href="/search?mode=pick&amp;context=2770&amp;tt=39" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Planetary Science</a>,</div><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;tt=42" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Astrobiology</a>,</div></div></div><div class="field field-name-field-topic-editor-pick-ref field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;ep=2770" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Cassini mission to Saturn</a></div></div></div><div class="field field-name-field-sn-subtitle">
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<h2>After 20 years, nearly 300 orbits and pioneering discoveries, the spacecraft plunges to its death in Saturn’s atmosphere</h2>
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<span itemprop="name"><a href="/author/lisa-grossman?mode=pick&amp;context=2770">Lisa Grossman</a></span> </div>
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<span class="field-content">9:08am, September 15, 2017</span> </div>
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</div></div></div></div><div class="field field-name-field-op-main-image field-type-image field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:associatedMedia schema:associatedMedia" resource="https://www.sciencenews.org/sites/default/files/2017/09/main/articles/091417_LG_cassini_death_main.jpg"><img typeof="foaf:Image" src="https://www.sciencenews.org/sites/default/files/2017/09/main/articles/091417_LG_cassini_death_main.jpg" width="860" height="460" alt="Illustration of Cassini&#039;s death" /></div></div></div><div class="field field-name-field-op-caption field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p><strong>BLAZE OF GLORY</strong> Cassini burned up like a comet above Saturn’s cloud tops just before 5 a.m. PDT on September 15. This artist’s illustration shows what it may have looked like.</p></div></div></div><div class="field field-name-field-sn-copyright field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>JPL-Caltech/NASA</p></div></div></div><div class="field field-name-field-article-citation field-type-text-long field-label-above">
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<div class="field-item even"><p><a href="https://www.sciencenews.org/editors-picks/cassini-mission-saturn">Editor’s pick: Cassini mission to Saturn</a></p></div>
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<div class="field-item even"><p>L. Grossman. <a href="https://www.sciencenews.org/article/saturn-cassini-curtain-call">As Cassini’s tour of Saturn draws to a close, a look back at postcards from the probe</a>. <em>Science News</em>. Vol. 192, September 2, 2017, p. 16.</p><p>L. Grossman. <a href="https://www.sciencenews.org/blog/science-ticker/titan-flyby-cassini-saturn-collision?tgt=nr">Final flyby puts Cassini on a collision course with Saturn</a>. Science News Online, September 11, 2017.</p><p>A. Yeager. <a href="https://www.sciencenews.org/blog/science-ticker/grand-finale-cassini-spacecraft-sets-collision-course-saturn">In ‘grand finale,’ Cassini spacecraft sets off on collision course with Saturn</a>. Science News Online, April 21, 2017.</p></div>
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<p><strong>PASADENA, Calif.</strong> — Cassini went down fighting.</p><p>After 20 years in space and 13 years orbiting Saturn, the veteran spacecraft spent its last 90 seconds or so firing its thrusters as hard as it could to keep sending Saturnian secrets back to Earth for as long as possible.</p><p>The spacecraft entered Saturn’s atmosphere at about 3:31 a.m. PDT on September 15 and immediately began running through all of its stabilizing procedures to try to keep itself upright. The signal that Cassini had reached its destination arrived at Earth at 4:54 a.m., and cut out about a minute later as the spacecraft lost its battle with Saturn’s atmosphere.</p><p>“The signal from the spacecraft is gone, and within the next 45 seconds, so will be the spacecraft,” Cassini project manager Earl Maize announced from the mission control center at NASA’s Jet Propulsion Lab. “I hope you’re all as deeply proud of this amazing accomplishment. Congratulations to you all. This has been an incredible mission, an incredible spacecraft, and you’re all an incredible team. I’m going to call this the end of mission. Project manager, off the net.”</p><p>With that, the mission control team erupted in applause, hugs and some tears.</p><p><img alt="" class="caption" src="/sites/default/files/2017/09/091517_lg_cassinifinale_missioncontrolhugs.jpg" style="width: 730px; height: 319px;" title=" Cassini team members Earl Maize (left) and Julie Webster embrace after the announcement that Cassini’s signal had been lost, signifying the end the mission. ~~ Joel Kowsky/NASA" /></p><p>It’s the end of an era. But the spacecraft’s last moments at Saturn will answer questions that couldn’t have been addressed any other way.</p><p>Going out in a blaze of glory seems fitting. Since its launch in 1997, the probe traveled a total of 7.9 billion kilometers. It gathered more than 635 gigabytes of science data and took more than 450,000 images. It completed 294 orbits of Saturn, discovered six named moons and made 162 close, deliberate flybys of the ringed planet’s largest and most interesting moons.</p><p><img alt="" class="caption" src="/sites/default/files/2017/09/091517_lg_cassinifinale_titan.jpg" style="float: right; width: 370px; height: 370px;" title="The thick atmosphere around Saturn’s moon Titan gives it a hazy appearance. Cassini made more than 100 flybys of Titan during its mission. ~~ JPL-Caltech/NASA, Space Science Institute" />The last flyby sealed Cassini’s fate. On September 11, at 12:04 p.m., Cassini passed by Saturn’s largest moon Titan one last time (<a href="https://www.sciencenews.org/blog/science-ticker/titan-flyby-cassini-saturn-collision?tgt=nr"><em>SN Online: 9/11/17</em></a>). The moon’s gravity nudged Cassini on an irretrievable trajectory into the giant planet’s atmosphere.</p><p>Also blame the moons — particularly lake-dappled Titan and watery Enceladus — for why Cassini went out in such dramatic fashion. The mission team decided to sacrifice the spacecraft when it ran out of fuel, rather than risk a collision with one of those potentially habitable moons and contaminating it with any still-lingering earthly microbes.</p><p>“Because of planetary protection and our desire to go back to Enceladus, go back to Titan, go back to the Saturn system, we must protect those bodies for future exploration,” Jim Green, director of NASA’s planetary science division, said at a news conference on September 13.</p><p>Even in its months-long death spiral, Cassini collected unprecedented observations. Starting in April, the spacecraft made 22 dives through the unexplored region between Saturn and its rings. Measurements of the gravity and composition in that zone will help solve outstanding mysteries. How long is Saturn’s day? How much material is in the rings? When and how did the rings form?</p><p>To answer that last question in particular, “you have to fly between the planet and the rings,” says planetary scientist Matthew Hedman of the University of Idaho in Moscow, who uses Cassini data to study the rings. “That’s risky. We had to wait until the end of the mission to take that risk.”</p><p><img alt="" class="caption" src="/sites/default/files/2017/09/091517_lg_cassinifinale_ringscape_730.jpg" style="width: 730px; height: 477px;" title="Saturn’s rings were a frequent target for Cassini’s cameras. This image was among the last the probe captured. ~~ JPL-Caltech/NASA, Space Science Institute" /></p><p>On September 13 and 14, Cassini took a last look around the Saturn system’s greatest hits, taking a color mosaic image of Saturn and the rings, a movie sequence of Enceladus setting behind Saturn, Titan and tiny moonlets in the rings that pull the icy ring particles around themselves to form features called propellers.</p><p>Inside the mission control center on the afternoon of September 14, a hushed operations team waited for Cassini to come online for the last time to start sending the last pictures back (<em><a href="https://www.sciencenews.org/blog/science-ticker/these-are-cassinis-parting-shots-saturn-system?tgt=nr">SNOnline: 9/15/17</a></em>). Then flight engineer Michael Staab at JPL suddenly broke the silence. “Yeah!” he yelled, pumping both arms in the air. Cassini’s last signal had just come in.</p><p>“That tells us that the spacecraft is nice and healthy, she’s doing just fine. She’s doing exactly what she’s supposed to do, like she’s done for 13 years,” Staab said. “We’re just gonna track her now, all the way in.”</p><p><img alt="" class="caption" src="/sites/default/files/2017/09/091517_lg_cassinifinale_daphnis.jpg" style="width: 730px; height: 400px;" title="The tiny moon Daphnis lurks within Saturn’s rings in a feature called Keeler Gap. Its gravity raises waves in the surrounding rings. ~~ JPL-Caltech/NASA, Space Science Institute" /></p><p>In the wee hours of September 15, the spacecraft reconfigured itself to shift from a recording device to a transmitting probe. As of that moment, its last and only job was to stream everything it could sense directly back to Earth in real time. Turning so that its ion neutral mass spectrometer was facing directly towards Saturn, Cassini could taste the atmosphere for the first time and investigate a phenomenon called “ring rain,” in which water and ice from the rings splash into the atmosphere. This idea was introduced in the early 1980s, but Cassini has already shown that it’s more complicated than previously thought.</p><p>“We’re trying to find out exactly what is coming from the rings and what is due to the atmosphere,” Hunter Waite, Cassini team lead for the mass spectrometer instrument and an atmospheric scientist at the Southwest Research Institute in San Antonio, said at the Sept. 13 news conference. “That final plunge will allow us to do that.” </p><p><img alt="" class="caption" src="/sites/default/files/2017/09/091517_lg_cassinifinale_enceladus.gif" style="width: 370px; height: 364px; float: right;" title="The ocean-covered moon Enceladus disappears behind Saturn in this animation of images taken by Cassini. ~~ JPL-Caltech/NASA, Space Science Institute" />That plunge happened at about 3:31 a.m., when Cassini entered the atmosphere about 10 degrees north of the equator, falling at around 34 kilometers per second. It took data constantly, directly measuring the temperature, magnetic field, plasma density and composition of the upper layers of Saturn’s atmosphere for the first time ever.</p><p>When it hit the atmosphere, Cassini started firing its thrusters to keep its antenna pointed at Earth despite the forces of the atmosphere trying to knock it askew. But about a minute later, the atmosphere won, when Cassini was about 1,400 kilometers above the cloud tops.</p><p>What happened next, scientists can only imagine. Models suggest this fiery demise: The spacecraft attempted to stabilize itself, but to no avail. It started to tumble faster and faster. Atmospheric friction broke the spacecraft apart, bit by bit — first its thermal blankets burned off, then aluminum components started to melt. The spacecraft probably fell another 1,000 kilometers as it disintegrated like a meteor, Maize said.</p><p>Saturn’s atmosphere crushed and melted the bits and pieces, until they completely dissociated and became part of the very planet the spacecraft had been sent to observe. </p><p>When all was said and done, the spacecraft lasted about 30 seconds longer than expected. That may help ensure the team got enough data to figure out Saturn’s rotation period, science team member Michele Dougherty of Imperial College London said at a post-mission news conference September 15. “I’m hoping we can do it, I’m not going to promise. Ask me in three months’ time.”</p><p>There are no planned future missions to Saturn, although some Cassini alumni are already working on proposals.</p><p><img alt="" class="caption" src="/sites/default/files/2017/09/091517_lg_cassinifinale_IR_730.jpg" style="width: 730px; height: 402px;" title="This infrared image shows where the Cassini spacecraft entered Saturn’s atmosphere on September 15. ~~JPL-Caltech/NASA, Space Science Institute" /></p><p>Outer solar system astronomers are now setting their sights on Jupiter and its icy, possibly life-friendly moons. The European Space Agency’s Jupiter Icy Moons Explorer (JUICE) and NASA’s Europa Clipper both hope to launch around 2022. Those missions may pave the way for a lander on Europa (<a href="https://www.sciencenews.org/article/europa-lander-mission-takes-another-step-toward-reality"><em>SN Online: 2/18/17</em></a>), which could directly look for life in that moon’s subsurface seas.</p><p>Planetary scientist Kevin Hand at JPL, who is leading the science definition team for the proposed Europa lander, feels a debt to Cassini.</p><p>“When you’re at the earliest frontiers of exploration, it’s hard to feel sad,” he said. “The wake we’re experiencing right now for Cassini, it’s not so much an end but the early steps that pave the way for the next stage of exploration.”</p><p>Even Maize is more proud than mourning.</p><p>“This is exactly the way we always planned it. It’s sad that we’re losing this incredible discovery machine,” he said in the moments leading up to Cassini’s disintegration. “But the real sense here is just, all right, we got it!”</p><p><img alt="" class="caption" src="/sites/default/files/2017/09/091417_LG_cassini_death_inline_730.jpg" style="width: 730px; height: 308px;" title="&lt;b&gt;FIRING AWAY&lt;/b&gt; Thrusters on Cassini (illustrated) fired at full power to keep it stable in Saturn’s atmosphere and help it send data to Earth for as long as possible. ~~ JPL-Caltech/NASA" /></p><hr /><p><em>Editor's note: This story was updated at 11:05 a.m. EDT on September 15 to incorporate updated information from a news conference. </em></p><span property="rnews:name schema:name" content="R.I.P. Cassini" class="rdf-meta element-hidden"></span>Thu, 14 Sep 2017 22:31:37 +0000Helen194058 at https://www.sciencenews.orgThe Cassini probe dies tomorrow. Here’s how to follow its endhttps://www.sciencenews.org/blog/science-ticker/cassini-probe-dies-tomorrow-heres-how-follow-its-end?mode=pick&context=2770
<div class="field field-name-field-op-blogpost-blog field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even">Science Ticker</div></div></div><div class="field field-name-field-op-section-term field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;tt=39" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Planetary Science</a>,</div></div></div><div class="field field-name-field-topic-editor-pick-ref field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;ep=2770" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Cassini mission to Saturn</a></div></div></div><div class="field field-name-field-op-author field-type-node-reference field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:creator schema:creator"><div class="view view-openpublish-related-content view-id-openpublish_related_content view-display-id-block_1 view-dom-id-a3b6b5af5689589bf9cdc9c329465f83">
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<div class="views-field views-field-field-profile-photo"> <div class="field-content"><a href="/author/helen-thompson?mode=pick&amp;context=2770"><img typeof="foaf:Image" src="https://www.sciencenews.org/sites/default/files/styles/author_thumbnail/public/2017/01/profiles/photos/Thompson_Helen.jpg?itok=KAZJZWOM" width="50" height="50" alt="Helen Thompson" /></a></div> </div>
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<span itemprop="name"><a href="/author/helen-thompson?mode=pick&amp;context=2770">Helen Thompson</a></span> </div>
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<div class="views-field views-field-published-at"> <span class="field-content">2:30pm, September 14, 2017</span> </div> </div>
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</div></div></div></div><div class="field field-name-field-op-main-image field-type-image field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:associatedMedia schema:associatedMedia" resource="https://www.sciencenews.org/sites/default/files/2017/09/main/blogposts/091417_ht_cassiniwatch_main.jpg"><img typeof="foaf:Image" src="https://www.sciencenews.org/sites/default/files/2017/09/main/blogposts/091417_ht_cassiniwatch_main.jpg" width="860" height="460" alt="Cassini at Saturn" /></div></div></div><div class="field field-name-field-op-caption field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>Cassini isn’t long for this world. But don’t worry, there are plenty of ways to track the spacecraft’s final hours.</p></div></div></div><div class="field field-name-field-sn-copyright field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>JPL-Caltech/NASA</p></div></div></div><p><a href="#video">View live feed</a></p><p>It’s not every day that a spacecraft gets vaporized by the very planet it sought to explore.</p><p><a href="https://www.youtube.com/watch?v=Z53ms70zDgk">After 13 years studying Saturn and its moons</a>, NASA’s Cassini spacecraft will plunge into the ringed gas giant’s atmosphere. The mission will come to a close at about 7:55 a.m. EDT (4:55 a.m. PDT) Friday, when Saturn’s atmosphere pushes Cassini’s antenna away from Earth, terminating the signal. Shortly thereafter, the spacecraft <a href="https://www.youtube.com/watch?v=sXVMGYS9Xxs">will disintegrate</a>.</p><p><a name="video" id="video"></a></p><p>If you want to keep tabs on the action, you’ve got a few options. <em>Science News</em> astronomy writer Lisa Grossman is at the Jet Propulsion Laboratory in Pasadena, Calif. — home of mission control for the Cassini probe. She’ll be popping on to <a href="https://www.facebook.com/sciencenews">the <em>Science News </em>Facebook page</a> throughout the day Thursday with live updates, and she (<a href="https://twitter.com/astrolisa?lang=en">@astrolisa</a>) and <em>Science News</em> <a href="https://twitter.com/sciencenews">(@ScienceNews</a>) will have details for you on Twitter as well.</p><p>Cassini’s death won’t be captured on film. But thanks to the internet, you can watch NASA scientists react to the probe’s impending doom live. In the early hours of Friday morning (7-8:30 a.m. EDT/4-5:30 a.m. PDT), NASA <a href="https://www.nasa.gov/nasalive">plans to stream a live video feed</a> from the control room, which you can watch here:</p><p><iframe allowfullscreen="" frameborder="0" height="411" src="https://www.youtube.com/embed/wwMDvPCGeE0?rel=0" width="730"></iframe></p><p>And, you can also watch on NASA JPL’s <a href="https://www.youtube.com/nasajpl/">YouTube</a> channel and NASA’s <a href="https://www.facebook.com/NASA">Facebook</a> page.</p><p>For more on Cassini’s exploits, check out all of <a href="https://www.sciencenews.org/search?ep=2770">our past coverage of the mission</a>.</p><span property="rnews:name schema:name" content="The Cassini probe dies tomorrow. Here’s how to follow its end" class="rdf-meta element-hidden"></span>Thu, 14 Sep 2017 17:41:53 +0000Helen194050 at https://www.sciencenews.orgSo long, Titan. Cassini snaps parting pics of Saturn’s largest moonhttps://www.sciencenews.org/blog/science-ticker/so-long-titan-cassini-snaps-parting-pics-saturn-moon?mode=pick&context=2770
<div class="field field-name-field-op-blogpost-blog field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even">Science Ticker</div></div></div><div class="field field-name-field-op-section-term field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;tt=37" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Astronomy</a>,</div><div class="field-item odd"><a href="/search?mode=pick&amp;context=2770&amp;tt=39" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Planetary Science</a>,</div></div></div><div class="field field-name-field-topic-editor-pick-ref field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;ep=2770" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Cassini mission to Saturn</a></div></div></div><div class="field field-name-field-op-author field-type-node-reference field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:creator schema:creator"><div class="view view-openpublish-related-content view-id-openpublish_related_content view-display-id-block_1 view-dom-id-fc9c774af3329f4ae2bb1272e16f2a96">
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<span itemprop="name"><a href="/author/lisa-grossman?mode=pick&amp;context=2770">Lisa Grossman</a></span> </div>
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<div class="views-field views-field-published-at"> <span class="field-content">4:05pm, September 13, 2017</span> </div> </div>
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</div></div></div></div><div class="field field-name-field-op-main-image field-type-image field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:associatedMedia schema:associatedMedia" resource="https://www.sciencenews.org/sites/default/files/2017/09/main/blogposts/091317_lg_titanlastkiss_option2.jpg"><img typeof="foaf:Image" src="https://www.sciencenews.org/sites/default/files/2017/09/main/blogposts/091317_lg_titanlastkiss_option2.jpg" width="860" height="460" alt="Titan&#039;s lake region" /></div></div></div><div class="field field-name-field-op-caption field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p><strong>IN THE REARVIEW WINDOW</strong> A final image of Saturn’s moon Titan (like one shown here from the Cassini spacecraft’s last distant flyby September 11) will be among the “final picture postcards of the Saturn system … to put in our Cassini scrapbook,” Linda Spilker, head scientist for the Cassini mission, said in a news conference September 13.</p></div></div></div><div class="field field-name-field-sn-copyright field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>Space Science Institute/JPL-Caltech/NASA</p></div></div></div><p>The Cassini spacecraft has snapped its penultimate pics of Saturn’s moon Titan.</p><p>This image, shot September 11 as Cassini <a href="https://www.sciencenews.org/blog/science-ticker/titan-flyby-cassini-saturn-collision">swung past the moon</a> at a distance of about 119,049 kilometers, shows Titan’s lake region near its north pole. “The haze has cleared remarkably as the summer solstice has approached,” Cassini Project Scientist Linda Spilker said in a news conference September 13.</p><p>Cassini performed 127 close flybys of Titan over the course of its 13-year mission, and used the moon’s gravity to adjust its trajectory each time. Those gravity assists let the team create a full global map of Titan.</p><p>Future engineers will borrow that trick to explore Jupiter’s moon Europa with the <a href="https://www.nasa.gov/feature/jpl/nasa-mission-named-europa-clipper">Clipper mission</a>, which is planned to launch in the 2020s. “Cassini pioneered that whole concept,” Jim Green, head of NASA’s planetary science division director, said at the news conference. </p><p>On this final pass, Titan’s gravity had one last job. It nudged Cassini on its final trajectory: <a href="https://www.sciencenews.org/blog/science-ticker/grand-finale-cassini-spacecraft-sets-collision-course-saturn">making a beeline for Saturn</a>. Tomorrow, the probe will spend its last full day in space snapping images of its greatest hits: Saturn and the rings, Titan, a small moon forming within the rings informally dubbed “Peggy,” the moon Enceladus, ring ripples called propellers and finally, the location of its own demise. The <a href="https://www.youtube.com/watch?v=sXVMGYS9Xxs">spacecraft will disintegrate</a> above the gas giant’s cloud tops early in the morning of September 15.</p><span property="rnews:name schema:name" content="So long, Titan. Cassini snaps parting pics of Saturn’s largest moon" class="rdf-meta element-hidden"></span>Wed, 13 Sep 2017 19:55:23 +0000Helen194034 at https://www.sciencenews.orgFinal flyby puts Cassini on a collision course with Saturnhttps://www.sciencenews.org/blog/science-ticker/titan-flyby-cassini-saturn-collision?mode=pick&context=2770
<div class="field field-name-field-op-blogpost-blog field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even">Science Ticker</div></div></div><div class="field field-name-field-op-section-term field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;tt=37" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Astronomy</a>,</div><div class="field-item odd"><a href="/search?mode=pick&amp;context=2770&amp;tt=39" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Planetary Science</a>,</div></div></div><div class="field field-name-field-topic-editor-pick-ref field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;ep=2770" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Cassini mission to Saturn</a></div></div></div><div class="field field-name-field-op-author field-type-node-reference field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:creator schema:creator"><div class="view view-openpublish-related-content view-id-openpublish_related_content view-display-id-block_1 view-dom-id-5ece1c54496b305f6a6a3b2a65b18737">
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<span itemprop="name"><a href="/author/lisa-grossman?mode=pick&amp;context=2770">Lisa Grossman</a></span> </div>
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<div class="views-field views-field-published-at"> <span class="field-content">4:00pm, September 11, 2017</span> </div> </div>
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</div></div></div></div><div class="field field-name-field-op-main-image field-type-image field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:associatedMedia schema:associatedMedia" resource="https://www.sciencenews.org/sites/default/files/2017/09/main/blogposts/091117_LG_cassini_ticker_main.jpg"><img typeof="foaf:Image" src="https://www.sciencenews.org/sites/default/files/2017/09/main/blogposts/091117_LG_cassini_ticker_main.jpg" width="860" height="460" alt="Cassini image of Saturn&#039;s moon Titan" title="Titan, a moon of Saturn" /></div></div></div><div class="field field-name-field-op-caption field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p><b>IN THE REARVIEW</b> On September 11, Saturn’s largest moon, Titan (shown in an image taken May 29), nudged the Cassini spacecraft onto its final trajectory. The probe will plunge into Saturn’s atmosphere on September 15.</p></div></div></div><div class="field field-name-field-sn-copyright field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>JPL-Caltech/NASA, Space Science Institute</p></div></div></div><p><a href="#video">View video</a></p><p>After one last swing past Titan, the Cassini spacecraft is now plunging to its doom. At 3:04 p.m. EDT (12:04 p.m. PDT) on September 11, the spacecraft used a gravitational nudge from Saturn’s largest moon to set itself on a collision course with the giant planet’s atmosphere on September 15.</p><p>Cassini’s last close flyby of <a href="https://www.sciencenews.org/blog/science-ticker/bubbles-may-put-mysterious-fizz-titans-polar-sea">Titan</a> on April 21 curved the spacecraft’s orbit to send it on a <a href="https://www.sciencenews.org/blog/science-ticker/grand-finale-cassini-spacecraft-sets-collision-course-saturn">series of dives between Saturn and its rings</a>. That approach took the probe to about 979 kilometers above the moon’s surface. This final flyby, which the mission team calls the “kiss goodbye,” is a more distant 119,049 kilometers — but that’s enough to slow the spacecraft down and send it into Saturn’s atmosphere, where it will ultimately melt and disintegrate.</p><p>“There is no coming out of it,” Cassini project manager Earl Maize said in a press conference on August 29. “That final kiss goodbye, I don’t want to get too romantic about it, but that really is our last flyby.”</p><p>Titan is home to lakes and rivers made of liquid hydrocarbons, which may be hospitable to life unlike that on Earth. Mission engineers decided to send Cassini to burn up in Saturn’s atmosphere in part to protect any potential life-forms from contamination if Cassini accidentally crashed into Titan.</p><p><a name="video" id="video"></a></p><p>Cassini has been orbiting Saturn since 2004 and <a href="https://www.sciencenews.org/article/saturn-cassini-curtain-call">has revolutionized our understanding of Saturn’s atmosphere, rings, moons</a>, and of the outer solar system in general.</p><div class="clearfix" style="margin: 0px; margin-top: 10px; margin-right: 0px; margin-bottom: 15px; margin-left: 10px; float:right; background:black;"><table border="0" width="350"><tbody><tr style="background:#000000;"><td><iframe allowfullscreen="" frameborder="0" height="411" src="https://www.youtube.com/embed/sXVMGYS9Xxs?rel=0" width="730"></iframe></td></tr><tr style="background:#000000;"><td><p style="background:#000000; color:#ffffff;padding:0 8px; font-size:13px;font-family:Lato, Helvetica,Verdana, sans-serif; font-weight:300;line-height:15px;position:relative;"><b>FINAL COUNTDOWN</b> Lead propulsion engineer Todd Barber outlines what to expect from the final days of the Cassini mission. <span style="text-align:right;color:#aaaaaa;text-transform:uppercase;font-size:10px; position:absolute;right:0;top:45px;"> </span></p></td></tr></tbody></table></div><script type="text/javascript" src="https://www.sciencenews.org/web-assets/js/video-fix.js"></script><span property="rnews:name schema:name" content="Final flyby puts Cassini on a collision course with Saturn" class="rdf-meta element-hidden"></span>Mon, 11 Sep 2017 19:25:40 +0000Kate194018 at https://www.sciencenews.orgAs Cassini’s tour of Saturn draws to a close, a look back at postcards from the probehttps://www.sciencenews.org/article/saturn-cassini-curtain-call?mode=pick&context=2770
<div class="field field-name-field-article-type field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even">Feature</div></div></div><div class="field field-name-field-op-section-term field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;tt=37" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Astronomy</a>,</div><div class="field-item odd"><a href="/search?mode=pick&amp;context=2770&amp;tt=39" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Planetary Science</a>,</div></div></div><div class="field field-name-field-topic-editor-pick-ref field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;ep=2770" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Cassini mission to Saturn</a></div></div></div><div class="field field-name-field-sn-subtitle">
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<h2>NASA's veteran spacecraft has revealed a lot about Saturn in its more than 20 years in space</h2>
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<span itemprop="name"><a href="/author/lisa-grossman?mode=pick&amp;context=2770">Lisa Grossman</a></span> </div>
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<span class="field-content">3:45pm, August 23, 2017</span> </div>
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</div></div></div></div><div class="field field-name-field-op-main-image field-type-image field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:associatedMedia schema:associatedMedia" resource="https://www.sciencenews.org/sites/default/files/2017/08/main/articles/090217_cassini_main.jpg"><img typeof="foaf:Image" src="https://www.sciencenews.org/sites/default/files/2017/08/main/articles/090217_cassini_main.jpg" width="1200" height="500" alt="Saturn, as photographed about Cassini" /></div></div></div><div class="field field-name-field-op-caption field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p><strong>CASSINI'S CURTAIN CALL</strong> In 13 years of orbiting Saturn, the Cassini spacecraft has seen the passing of two seasons: northern winter to spring and spring to summer. In this March 2016 image, Saturn's northern summer solstice is approaching. </p></div></div></div><div class="field field-name-field-sn-copyright field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>JPL-Caltech/NASA, Space Science Institute</p></div></div></div><div class="field field-name-field-magazine-ref field-type-node-reference field-label-hidden"><div class="field-items"><div class="field-item even"><div class="view view-article-issue-info view-id-article_issue_info view-display-id-block view-dom-id-00f083b54cc2b24c16b092d4d64bf006">
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<div class="views-field views-field-field-magazine-ref"> <span class="views-label views-label-field-magazine-ref">Magazine issue: </span> <span class="field-content"><a href="https://www.sciencenews.org/sn-magazine/september-2-2017?mode=pick&amp;context=2770">Vol. 192 No. 3, September 2, 2017, p. 16</a></span> </div> </div>
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</div></div></div></div><div class="narrow-column"><p><font size="20">T</font><span style="font-size:18px">ake a bow, Cassini. It’s been a marathon performance: 20 years in space, more than 200 orbits around Saturn, and hundreds of thousands of images of the giant planet, its splashy rings and its many moons. On September 15, the veteran spacecraft will use its last burst of fuel to plunge into the sixth planet from the sun. Scientists and space enthusiasts around the world will watch it go with awe and nostalgia.</span></p><p>“It’s hard not to anthropomorphize the spacecraft,” says Matthew Tiscareno of the SETI Institute in Mountain View, Calif., who has been working on Cassini since it entered Saturn’s orbit in 2004. “We’ve been riding on its back for these 13 years, and it’s done everything we’ve asked. I think it’s the most spectacularly successful mission that NASA has ever run.”</p></div><p><img alt="" class="caption" src="/sites/default/files/2017/08/090217_cassini_inline1.jpg" style="width: 1180px; height: 544px;" title="&lt;b&gt;AN ICY TRACK&lt;/b&gt; Cassini showed that Saturn’s celebrated rings are more like a Roller Derby track than a record album. Chunks of ice as small as sand and larger than houses zip and collide, guided by the gravity of Saturn itself, as well as some of its small moons. A ring disturbance photographed on April 8, 2016, (in the outer ring below) was most likely due to a small embedded object rather than the pull of the tiny bystander of a moon Pandora (bottom right). ~~ JPL-Caltech/NASA, Space Science Institute" /></p><div class="narrow-column"><p>Cassini was designed to train its 12 scientific instruments on the Saturn system for a short four years, but NASA extended the mission twice. Even with the extra time, Cassini’s 13-year run is less than half of a year on Saturn, where a year lasts 29 Earth years.</p></div><div class="inline-content inline-content-right clearfix"><h4>Gas swirl</h4><div class="inline-content-copy"><p><img alt="" class="caption" src="/sites/default/files/2017/08/090217_cassini_hexaxon_inline_370.gif" style="width: 370px; height: 370px;" title="~~ JPL-Caltech/NASA, Space Science Institute" /></p><p>Saturn’s north pole was dark when Cassini arrived in 2004. But as the seasons changed, light illuminated a bizarre six-sided swirl of gases at the pole (shown here in false color). The hexagon, known since the 1980s, is about 30,000 kilometers wide with a massive hurricane centered on the north pole (<a href="https://www.sciencenews.org/article/saturn%E2%80%99s-six-sided-cloud-pattern-gets-close-look"><em>SN: 1/11/14, p. 10</em></a>).</p></div></div><div class="narrow-column"><p>After all this time, we’ve witnessed only the transitions to Saturnian spring and summer, the equivalent of January to June on Earth. And yet we’ve seen so much.</p><p>Cassini has revealed massive churning storms that rage for decades, rings that may be the best laboratory for studying how planets form and details of some of Saturn’s more than 60 moons. Two of those satellites, Titan and Enceladus, surprised Cassini scientists by having <a href="https://www.sciencenews.org/article/potential-ingredient-alien-life-found-titan">many of the right ingredients for life</a> (<em>SN: 9/2/17, p. 12</em>). The craft has revamped our picture of Saturn and its celestial family.</p><p>Saturn’s potentially habitable moons are the reason Cassini must meet a dramatic end. The Cassini mission team decided it was safer to crash the craft into Saturn itself than to risk the craft wandering off and brushing up against Enceladus or Titan, spreading its earthly germs to any nascent ecosystems there.</p><p>But the craft will be busy until the very end. Since April, Cassini has been making weekly dives into the possibly rubble-strewn region between Saturn and its rings, a zone the team hadn’t dared explore before. Plus, the craft will collect data during its last hurtle into the gas giant’s atmosphere. Those final measurements should help solve some of the most basic mysteries about the planet, including when it got its iconic rings.</p><p>“Cassini data,” says team member Ralph Lorenz of the Applied Physics Lab, “is going to keep us busy for decades.”</p></div><div class="narrow-column"><h3><strong>Surviving storm </strong></h3><p><img alt="" class="caption" src="/sites/default/files/2017/08/090217_cassini_inline2.jpg" style="width: 730px; height: 497px;" title="~~ JPL-Caltech/NASA, Space Science Institute" /></p><p>In the eye of Saturn’s hexagon swirl, cloud speeds can reach 150 meters per second. The storm, shown here in false color from 2012, has probably been there for decades, if not centuries. Saturn has no mountains or oceans to interrupt the storm.</p><h3><b>Raised ripples</b></h3><p><iframe allowfullscreen="" frameborder="0" height="411" src="https://www.youtube.com/embed/3cftya9AY9o?rel=0" width="730"></iframe></p><p>Saturn’s tiny moon Daphnis orbits within the 42-kilometer-wide Keeler Gap in Saturn’s outer A ring. This sequence of 10 images, each taken about one minute and 30 seconds apart, shows Daphnis’ gravitational pull perturbing the particles at the gap’s edge. The moon is only 8 kilometers across, but its gravitational pull is enough to raise ripples in the rings around it. These waves were first noticed in 2009, around the time of Saturn’s spring equinox. Daphnis has a ridge around its equator, which is probably made of fine particles it has gathered from the rings.</p><h3>Ring spikes</h3><p><img alt="" class="caption" src="/sites/default/files/2017/08/090217_cassini_inline3.jpg" style="width: 730px; height: 497px;" title="~~ JPL, NASA, Space Science Institute" /></p><p>Saturn’s rings are “arguably the flattest structure known to man,” says astronomer Matthew Tiscareno. Over a span of hundreds of thousands of kilometers, their vertical thickness typically varies by only about 10 meters. But Cassini snapped these structures, as tall as 2.5 kilometers, in 2009, when sunlight struck the rings at a perfect angle to cast long shadows.</p></div><h3>Lineup</h3><p><img alt="" class="caption" src="/sites/default/files/2017/08/090217_cassini_inline12.jpg" style="width: 1180px; height: 543px;" title="~~ JPL-Caltech/NASA, SSI" /></p><div class="narrow-column"><p>Cassini caught a family portrait of five of Saturn’s moons in this image from July 2011. From left to right, they are Janus (179 km across), Pandora (81 km across, nestled in the rings), Enceladus (504 km across, appearing half lit above the rings in the center of the image), Mimas (396 km across), and Rhea (1528 km across, to the far right).</p><h3>Titan terrain</h3><p><img alt="" class="caption" src="/sites/default/files/2017/08/090217_cassini_inline5.jpg" style="width: 730px; height: 497px;" title="~~ JPL-Caltech/NASA, ASI, Cornell" /></p><p>Cassini mission scientist Ralph Lorenz has this false color image of Ligeia Mare, a large sea on Saturn’s moon Titan, hanging in his office. Cassini’s radar peered through the moon’s thick orange haze to reveal an Earthlike surface with seas, rivers and clouds filled with liquid ethane and methane. The moon could possess the ingredients for life. “Titan has been doing prebiotic chemistry experiments for us for a huge amount of time,” says team member Elizabeth Turtle. She and Lorenz are working with others on a proposed mission called Dragonfly that would land drones on the moon to sample its surface.</p><p>Titan is the only place in the solar system other than Earth known to host long-lived liquid lakes and streams. But on Titan, the liquid is mostly methane and ethane, not water. The video below combines radar images of Titan from 2004 to 2013 as Cassini flies over its two largest seas, Kraken Mare and Legia Mare. Where the lakes look dark, the liquid is exceptionally still and flat as a mirror.</p><p><iframe allowfullscreen="" frameborder="0" height="411" src="https://www.youtube.com/embed/ho1VmvuChFU?rel=0" width="730"></iframe></p><h3><b>Inner orbits</b></h3><p><img alt="" class="caption" src="/sites/default/files/2017/08/090217_cassini_inline8.jpg" style="width: 730px; height: 497px;" title="~~ JPL-Caltech/NASA, Space Science Institute" /></p><p>By guiding tiny particles around themselves, small moons embedded in Saturn’s rings create the propeller-like features seen here. Scientists have followed these objects for over a decade, naming the larger ones after pioneers of aviation. These images, taken February 21, 2017, show two views of Santos-Dumont, named for a Brazilian-French aviator. “This is the only time in the history of astronomy that we’ve tracked the orbit of an object that is orbiting in a disk,” says astronomer Matthew Tiscareno. Studying the propellers can help reveal how planets forming in the disk of gas and dust around a young star grow.</p><h3><b>Icy jets</b></h3><p><iframe allowfullscreen="" frameborder="0" height="720" src="https://www.youtube.com/embed/5zvNvwLimP8?rel=0" width="1280"></iframe></p><p>One of the biggest surprises of the Cassini mission was that the icy moon Enceladus is spewing its guts into Saturn’s rings. These jets from the moon’s south pole come from a subsurface ocean, which may have the right chemistry for life. The jets also supply icy material to one of Saturn’s rings. </p><h3><b>Plume power</b></h3><p><img alt="" class="caption" src="/sites/default/files/2017/08/090217_cassini_inline10.jpg" style="width: 730px; height: 496px;" title="~~ JPL-Caltech/NASA, Space Science Institute" /></p><p>This false color image from 2005 shows the reach of the spectacular plumes on the moon Enceladus. Later sampling by Cassini revealed that the plumes contain ammonia, a variety of organic compounds and molecular hydrogen — all signs that the moon might be habitable. NASA is considering a mission to go back and sample the plumes.</p><div class="clearfix"><p><img alt="" class="caption" src="/sites/default/files/2017/08/090217_cassini_aurora_inline_370.gif" style="float:right; width: 370px; height: 370px;" title="~~ JPL-Caltech/NASA, SSI" /></p><h3>Southern lights</h3><p>Cassini spotted Saturn's shimmering aurora dancing near its south pole in July 2017. The bright spots shooting across this video from the bottom left are due to charged particles hitting the detector. Behind the spots, you can see the aurora's ghostly glow. These light shows are created when charged particles from the sun strike the planet’s atmosphere and make gas glow. </p></div><h3>Moon sculptor</h3><p><img alt="" class="caption" src="/sites/default/files/2017/08/090217_cassini_inline-slideshow4.jpg" style="width: 730px; height: 496px;" title="~~ JPL-Caltech/NASA, SSI, QMUL" /></p><p>Saturn's outer ring, called the F ring, is sculpted by tiny moons passing by the ring. The ring’s dust and ice particles are tugged by the moons’ gravity. These images from Cassini, taken between 2006 and 2008, show various disturbances in the outer ring.</p></div><h3><b>Mother Earth</b> </h3><p><img alt="" class="caption" src="/sites/default/files/2017/08/090217_cassini_inline7.jpg" style="width: 1180px; height: 544px;" title="~~ JPL-Caltech/NASA, Space Science Institute" /></p><div class="narrow-column"><p>This iconic Cassini image is known as “The Day the Earth Smiled.” On July 19, 2013, Cassini turned back toward its planet of origin and shot a picture with Saturn’s rings and Earth and its moon all in the same frame (<a href="https://www.sciencenews.org/article/cassini-photo-puts-earth-perspective"><em>SN: 8/24/13, p. 8</em></a>). It was the third time Earth was imaged from the outer solar system but the first time human­kind got a heads-up, so people could look up and smile or wave for the camera.</p><hr /><p><em>This article appears in the Sept. 2, 2017 issue of </em>Science News<em> with the headline, "Cassini's curtain call: The spacecraft that put Saturn and its moons in the spotlight bids adieu." </em></p><p><a href="https://www.sciencenewsforstudents.org/article/cassini-spacecraft-takes-its-final-bo"><em>Read another version of this story at </em>Science News for Students</a><em> </em></p></div>
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</style><script type="text/javascript" src="https://www.sciencenews.org/web-assets/js/video-fix.js"></script><span property="rnews:name schema:name" content="As Cassini’s tour of Saturn draws to a close, a look back at postcards from the probe" class="rdf-meta element-hidden"></span>Thu, 17 Aug 2017 14:51:00 +0000Helen193653 at https://www.sciencenews.orgThe first Cassini to explore Saturn was a person https://www.sciencenews.org/blog/context/first-cassini-explore-saturn-was-person?mode=pick&context=2770
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<h2>Space probe preparing to crash into ringed planet was named for an astronomical pioneer</h2>
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<div class="field field-name-field-op-blogpost-blog field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even">Context</div></div></div><div class="field field-name-field-op-section-term field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;tt=57" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">History of Science</a>,</div><div class="field-item odd"><a href="/search?mode=pick&amp;context=2770&amp;tt=37" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Astronomy</a>,</div></div></div><div class="field field-name-field-topic-editor-pick-ref field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;ep=2770" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Cassini mission to Saturn</a></div></div></div><div class="field field-name-field-op-author field-type-node-reference field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:creator schema:creator"><div class="view view-openpublish-related-content view-id-openpublish_related_content view-display-id-block_1 view-dom-id-3f2b31f672de5b93f0b490c6ab71edc3">
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<div class="views-field views-field-field-profile-photo"> <div class="field-content"><a href="/author/tom-siegfried?mode=pick&amp;context=2770"><img typeof="foaf:Image" src="https://www.sciencenews.org/sites/default/files/styles/author_thumbnail/public/profiles/photos/tom_siegfried_250.jpg?itok=EJeD8JPS" width="50" height="50" alt="" /></a></div> </div>
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<span itemprop="name"><a href="/author/tom-siegfried?mode=pick&amp;context=2770">Tom Siegfried</a></span> </div>
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<div class="views-field views-field-published-at"> <span class="field-content">7:00am, May 15, 2017</span> </div> </div>
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</div></div></div></div><div class="field field-name-field-op-main-image field-type-image field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:associatedMedia schema:associatedMedia" resource="https://www.sciencenews.org/sites/default/files/2017/05/main/blogposts/051217_TO_cassini_main_FREE.jpg"><img typeof="foaf:Image" src="https://www.sciencenews.org/sites/default/files/2017/05/main/blogposts/051217_TO_cassini_main_FREE.jpg" width="860" height="460" alt="Saturn" /></div></div></div><div class="field field-name-field-op-caption field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p><strong>TWO CASSINIS</strong> The Cassini spacecraft has become famous for its stunning views of Saturn, including this image of the unlit side of the rings taken in 2012. But what do we know about the man Cassini was named for?</p></div></div></div><div class="field field-name-field-sn-copyright field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>JPL-Caltech/NASA, Space Science Institute</p></div></div></div><p>As the Cassini spacecraft plunges toward its <a href="https://saturn.jpl.nasa.gov/">death on Saturn</a>, the world’s knowledge of the famous ringed planet continues to accumulate. Thanks to years of observations by the versatile probe, astronomers now know Saturn as intimately as macaroni knows cheese. But still hardly anyone outside the world of astronomy knows anything about Cassini — and I don’t mean the spacecraft, but the guy it was named for.</p><p><a href="http://www.encyclopedia.com/people/science-and-technology/astronomy-biographies/giovanni-domenico-cassini">Gian Domenico Cassini</a> was an Italian astronomer, born in Perinaldo in 1625, around the time that Galileo was battling the church over Copernicus’ revelation that the Earth orbits the sun. Cassini was attracted to poetry but was also good at math. He got his start in science via astrology, which back then was not considered quite as completely idiotic as it is today. In fact, astronomy itself was often supported by wealthy people in order to get better astrological forecasts. One such wealthy Italian, an amateur astronomer, was impressed with a pamphlet on astrology that Cassini had written; it earned him an invitation to work at the amateur’s observatory, near Bologna.</p><p>From the leading scientists at Bologna, Cassini learned the importance of using high-quality instruments to make the most precise measurements possible. His talents were soon recognized; by 1650 Cassini’s accomplishments and reputation earned him the chair in astronomy at the university in Bologna. He continued his research during the 1650s, taking a particular interest in comets.</p><p><img alt="" class="caption" src="/sites/default/files/2017/05/051217_TO_cassini_inline_370_FREE.jpg" style="float: right; width: 370px; height: 369px;" title="&lt;b&gt;EYES ON THE SKIES&lt;/b&gt; Gian Domenico Cassini was an Italian astronomer who studied comets, the sun and solar eclipses. After mastering the moons of Jupiter, he turned to Saturn.~~ Suisui/Wikimedia Commons" />Cassini was an old-school conservative kind of scientist, not even inclined to take Galileo’s side on the Earth-orbiting-the-sun issue. Cassini preferred <a href="http://www.encyclopedia.com/people/science-and-technology/astronomy-biographies/tycho-brahe">Tycho Brahe’s</a> position that the other planets orbited the sun, but the sun then orbited the Earth. (Later Cassini accepted the Copernican sun-centered solar system, but only half-heartedly.) Cassini also was no fan of Newton’s law of gravity.</p><p>Cassini’s work as an eminent Italian scientist was not limited to astronomy. Called on to referee a political dispute over the course of a river, he mastered hydraulics. Later he spent some time studying insects and experimenting on blood transfusions. None of that was as fun as astronomy, though, so he returned to the stars often. In addition to comets, he specialized in the sun and especially solar eclipses. Some of his best work resulted from the use of a meridian — a large sundial-like device for recording solar movements — that he designed and had installed on the top of a church steeple.</p><p>Cassini was also clever enough to know the value of cultivating useful friendships. In particular, he was on good terms with some skillful Roman lens makers who provided him with especially powerful telescopes. With such instruments Cassini was able to calculate the rotation rates of Jupiter and Mars accurately. (He gave Venus a shot, but it was harder.)</p><p>Even more impressively, Cassini accomplished a goal that had eluded Galileo by accurately describing the motions of the moons of Jupiter. It was Cassini’s work on Jupiter’s moons that allowed the Danish astronomer <a href="https://www.britannica.com/biography/Ole-Romer">Olaus Rømer</a> to measure the speed of light, establishing that light did not transit space instantaneously, as many (including Cassini) had believed.</p><p>Even before Rømer’s results, Cassini’s accomplishments made him famous enough to get offered a job in Paris. That job was actually a prime position with the new French Academy of Sciences, whose founders recruited savants from all over Europe to enhance the new academy’s prestige. So in 1669 Cassini moved to Paris. He didn’t fit in all that well; his French was sketchy and his authoritarian approach to things in general ticked some people off. But he eventually managed to develop a world-class astronomical observation program. He became a French citizen in 1673 and married the daughter of a French official wealthy enough to offer as part of the dowry a nice castle for a summer home. Cassini then forgot about his original plan to return to Italy and spent the rest of his life in France.</p><p><em>Story continues after image</em></p><p><img alt="" class="caption" src="/sites/default/files/2017/05/051217_TO_cassini_inline_2_730_FREE.jpg" style="width: 730px; height: 308px;" title="&lt;b&gt;FINAL DIVE&lt;/b&gt; Cassini the spacecraft, which has been exploring Saturn since 2004, will plunge into the planet's atmosphere in September 2017. ~~ JPL-Caltech/NASA" /></p><p>Had his astronomical achievements ended with his departure from Italy, Cassini would have been an odd choice for the name of a spacecraft sent to study Saturn. But besides his administrative role at the French academy’s observatory, Cassini continued his own studies. And, having mastered Jupiter, he naturally moved on to Saturn. In 1671 he discovered Saturn’s moon Iapetus and found another, Rhea, the next year. Much later he detected the moons Tethys and Dione. He also thoroughly examined the disk around Saturn and discerned that it was not just one ring. He identified two prominent rings separated by a small gap — the thin black band between the two is now known as Cassini’s division. Cassini even guessed, more or less correctly, that the rings are made of small particles all orbiting Saturn in concert.</p><p>And so Cassini knew Saturn as intimately as anyone from his era, establishing sufficient Saturnian credentials to earn the honor of having a space probe named for him. Cassini the probe has now seen Saturn much more clearly than Cassini the man. But soon Cassini the probe will die and go blind; Cassini the man first went blind, two years before he died, in 1712.</p><p><em>Follow me on Twitter: <a href="https://twitter.com/tom_siegfried">@tom_siegfried</a></em></p><span property="rnews:name schema:name" content="The first Cassini to explore Saturn was a person " class="rdf-meta element-hidden"></span>Thu, 11 May 2017 22:07:13 +0000Kate193242 at https://www.sciencenews.orgNitrogen fizz fuels ‘magic island’ on Titan, simulation suggestshttps://www.sciencenews.org/article/nitrogen-fizz-fuels-magic-island-titan-simulation-suggests?mode=pick&context=2770
<div class="field field-name-field-article-type field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even">News in Brief</div></div></div><div class="field field-name-field-op-section-term field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;tt=39" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Planetary Science</a>,</div></div></div><div class="field field-name-field-topic-editor-pick-ref field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;ep=2770" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Cassini mission to Saturn</a></div></div></div><div class="field field-name-field-op-author field-type-node-reference field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:creator schema:creator"><div class="view view-article-related-content view-id-article_related_content view-display-id-block_1 view-dom-id-bbd4627f319dfff225c9145ebe1cc5dd">
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<span class="field-content">11:00am, April 18, 2017</span> </div>
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</div></div></div></div><div class="field field-name-field-op-main-image field-type-image field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:associatedMedia schema:associatedMedia" resource="https://www.sciencenews.org/sites/default/files/2017/04/main/blogposts/041717_AY_titan_main.jpg"><img typeof="foaf:Image" src="https://www.sciencenews.org/sites/default/files/2017/04/main/blogposts/041717_AY_titan_main.jpg" width="860" height="460" alt="" /></div></div></div><div class="field field-name-field-op-caption field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p><strong>SHAPESHIFTER</strong> Nitrogen bubbles may be the source of an on-again, off-again bright spot, or “magic island,” on Saturn’s moon Titan. Cassini spacecraft images of the island, which sits in a hydrocarbon sea called Ligeia Mare, revealed the feature’s fickle nature.</p></div></div></div><div class="field field-name-field-sn-copyright field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>Cornell/ASI/JPL-Caltech/NASA</p></div></div></div><div class="field field-name-field-magazine-ref field-type-node-reference field-label-hidden"><div class="field-items"><div class="field-item even"><div class="view view-article-issue-info view-id-article_issue_info view-display-id-block view-dom-id-7ce55b049360497639218eb889ca814d">
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<div class="views-field views-field-field-magazine-ref"> <span class="views-label views-label-field-magazine-ref">Magazine issue: </span> <span class="field-content"><a href="https://www.sciencenews.org/sn-magazine/may-13-2017?mode=pick&amp;context=2770">Vol. 191 No. 9, May 13, 2017, p. 17</a></span> </div> </div>
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</div></div></div></div><p>Saturn’s main moon, Titan, has a “magic island” that might be made of <a href="http://nature.com/articles/doi:10.1038/s41550-017-0102">streams of nitrogen bubbles</a>, scientists report April 18 in <em>Nature Astronomy</em>.</p><p>Images from NASA’s Cassini spacecraft show that the island, which appears as a bright spot, comes and goes. It sits in Ligeia Mare, a sea made of methane, ethane and nitrogen in Titan’s northern polar region. The sea is probably 100 to 200 meters deep and frigid, about –183° to –193° Celsius.</p><p>The sea may also be stratified, with more ethane in the deeper layers and methane near the surface. If currents occasionally pull methane down to the deeper sea, the methane and ethane can mix, simulations by Daniel Cordier of the University of Reims Champagne-Ardenne in France and colleagues suggest. Nitrogen doesn’t like this combo, so the gas would separate out of the liquid, fizzing back to the sea surface in centimeter-sized bubbles.</p><p>Cassini had one last chance to search for signs of bubbles or some other explanation for the island when it flew by Titan a final time on April 22 (<a href="https://www.sciencenews.org/blog/science-ticker/grand-finale-cassini-spacecraft-sets-collision-course-saturn"><em>SN Online: 4/21/17</em></a>).</p><span property="rnews:name schema:name" content="Nitrogen fizz fuels ‘magic island’ on Titan, simulation suggests" class="rdf-meta element-hidden"></span>Fri, 28 Apr 2017 14:56:13 +0000Cassie193195 at https://www.sciencenews.orgCassini’s ring dive offers first close-up of Saturn’s cloud topshttps://www.sciencenews.org/article/cassinis-ring-dive-offers-first-close-saturns-cloud-tops?mode=pick&context=2770
<div class="field field-name-field-article-type field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even">News in Brief</div></div></div><div class="field field-name-field-op-section-term field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;tt=39" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Planetary Science</a>,</div></div></div><div class="field field-name-field-topic-editor-pick-ref field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;ep=2770" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Cassini mission to Saturn</a></div></div></div><div class="field field-name-field-sn-subtitle">
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<h2>Spacecraft images reveal stunning views of planet’s hurricane and more</h2>
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<span class="field-content">5:49pm, April 27, 2017</span> </div>
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</div></div></div></div><div class="field field-name-field-op-main-image field-type-image field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:associatedMedia schema:associatedMedia" resource="https://www.sciencenews.org/sites/default/files/2017/04/main/articles/042717_AY_saturn_main_free.jpg"><img typeof="foaf:Image" src="https://www.sciencenews.org/sites/default/files/2017/04/main/articles/042717_AY_saturn_main_free.jpg" width="860" height="460" alt="Saturn&#039;s atmosphere" /></div></div></div><div class="field field-name-field-op-caption field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p><strong>FIRST LOOK</strong> NASA’s Cassini spacecraft snapped these closest-ever views of Saturn’s atmosphere on April 26. The images show filamentary and cumulus clouds, along with a good view of the planet’s giant hurricane (middle).</p></div></div></div><div class="field field-name-field-sn-copyright field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>Space Science Institute, JPL-Caltech/NASA</p></div></div></div><div class="field field-name-field-article-citation field-type-text-long field-label-above">
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<div class="field-item even"><p><a href="https://saturn.jpl.nasa.gov/news/3032/nasa-spacecraft-dives-between-saturn-and-its-rings/">NASA spacecraft dives between Saturn and its rings</a>. JPL Media Release. Posted online April 27, 2017.</p></div>
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<div class="field-item even"><p><a href="https://saturn.jpl.nasa.gov/galleries/raw-images/">Cassini’s raw image gallery</a></p><p>A. Yeager. <a href="https://www.sciencenews.org/blog/science-ticker/grand-finale-cassini-spacecraft-sets-collision-course-saturn">In ‘grand finale,’ Cassini spacecraft sets off on collision course with Saturn</a>. Science News Online. April 21, 2017.</p><p>A. Yeager. <a href="https://www.sciencenews.org/article/food-microbes-found-enceladus">Food for microbes found on Enceladus</a>. Science News Online. April 13, 2017.</p><p>C. Crockett. <a href="https://www.sciencenews.org/blog/science-ticker/cassini-spacecraft-preps-one-last-flyby-enceladus">Cassini spacecraft preps for one last flyby of Enceladus</a>. Science News Online. December 18, 2015.</p><p>E. Wayman. <a href="https://www.sciencenews.org/article/snapshots-reveal-details-saturns-gigantic-hurricane">Snapshots reveal details of Saturn's gigantic hurricane</a>. Science News Online. April 30, 2013.</p><p>R. Cowen. <a href="https://www.sciencenews.org/node/12519">Huge cyclone churns at Saturn’s north pole</a>. <em>Science News</em>. Vol. 174, November 8, 2008, p. 9.</p></div>
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<p>Cassini has beamed back stunning images from the spacecraft’s daring dive between Saturn and its rings.</p><p>The first closeup pictures of the planet’s atmosphere reveal peculiar threadlike clouds and puffy cumulus ones, plus the giant hurricane first spotted on Saturn in 2008 (<a href="https://www.sciencenews.org/node/12519"><i>SN: 11/8/08, p. 9</i></a>). Released April 27, the images of Saturn’s cloud tops are a “big step forward” for understanding the planet’s atmosphere, says Cassini imaging team member Andy Ingersoll, an atmospheric scientist at Caltech.</p><p>“I was pretty struck by the prevalence of the filamentary type of clouds,” he says. “It’s as if the long threads of clouds refuse to mix with each other.” Studying the interactions of these clouds and the cumulus ones will reveal what’s going on in Saturn’s skies.</p><p>During its dive, Cassini swooped to within 3,000 kilometers of the planet’s atmosphere and 300 kilometers of the innermost edge of the rings at 124,000 kilometers per hour. Slamming into even tiny particles from the rings could have damaged the spacecraft. To protect Cassini, mission scientists used the spacecraft’s 4-meter-wide antenna as a shield, putting the spacecraft temporarily out of contact with NASA.</p><p>Cassini reestablished contact with mission control early on April 27 and started to send back data minutes later. Shots of the rings and other features will be available in the coming days, and more stunning views are expected when the spacecraft shoots through the gap between Saturn and its rings again on May 2. It will ultimately orbit 20 more times before plunging into the planet’s atmosphere on September 15 (<a href="https://www.sciencenews.org/blog/science-ticker/grand-finale-cassini-spacecraft-sets-collision-course-saturn"><i>SN Online: 4/21/17</i></a>).</p><span property="rnews:name schema:name" content="Cassini’s ring dive offers first close-up of Saturn’s cloud tops" class="rdf-meta element-hidden"></span>Thu, 27 Apr 2017 21:47:45 +0000Lillian193193 at https://www.sciencenews.orgNo long, twisted tail trails the solar systemhttps://www.sciencenews.org/article/no-long-twisted-tail-trails-solar-system?mode=pick&context=2770
<div class="field field-name-field-article-type field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even">News</div></div></div><div class="field field-name-field-op-section-term field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;tt=37" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Astronomy</a>,</div></div></div><div class="field field-name-field-topic-editor-pick-ref field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/search?mode=pick&amp;context=2770&amp;ep=2770" typeof="skos:Concept" property="rdfs:label skos:prefLabel" datatype="">Cassini mission to Saturn</a></div></div></div><div class="field field-name-field-sn-subtitle">
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<h2>Bubble inflated by particles from the sun is spherical, not comet-shaped, study shows</h2>
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<span itemprop="name"><a href="/author/ashley-yeager?mode=pick&amp;context=2770">Ashley Yeager</a></span> </div>
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<span class="field-content">11:00am, April 24, 2017</span> </div>
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</div></div></div></div><div class="field field-name-field-op-main-image field-type-image field-label-hidden"><div class="field-items"><div class="field-item even" rel="rnews:associatedMedia schema:associatedMedia" resource="https://www.sciencenews.org/sites/default/files/2017/04/main/articles/042117_AY_heliosphere_main.png"><img typeof="foaf:Image" src="https://www.sciencenews.org/sites/default/files/2017/04/main/articles/042117_AY_heliosphere_main.png" width="860" height="460" alt="heliosphere" /></div></div></div><div class="field field-name-field-op-caption field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p><strong>A TALE OF NO TAIL </strong>Data from the Voyager and Cassini spacecraft suggest that the heliosphere, the bubble of particles surrounding the solar system, is spherical, not comet-shaped. This illustration shows how that bubble is shaped by the interstellar magnetic field and flow of particles from interstellar space. Other labeled parts of the heliosphere are its outer edge (heliopause), the point at which the solar wind slows in speed (termination shock) and the region between those two boundaries (heliosheath).</p></div></div></div><div class="field field-name-field-sn-copyright field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>K. Dialynas <em>et al</em>/<em>Nature Astronomy</em> 2017</p></div></div></div><div class="field field-name-field-magazine-ref field-type-node-reference field-label-hidden"><div class="field-items"><div class="field-item even"><div class="view view-article-issue-info view-id-article_issue_info view-display-id-block view-dom-id-b788e407ace4b804c6a7e45ff9afdd1a">
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<div class="views-field views-field-field-magazine-ref"> <span class="views-label views-label-field-magazine-ref">Magazine issue: </span> <span class="field-content"><a href="https://www.sciencenews.org/sn-magazine/may-27-2017?mode=pick&amp;context=2770">Vol. 191 No. 10, May 27, 2017, p. 15</a></span> </div> </div>
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<div class="field-item even"><p>K. Dialynas et al. <a href="http://nature.com/articles/doi:10.1038/s41550-017-0115">The bubble-like shape of the heliosphere observed by Voyager and Cassini</a>. <em>Nature Astronomy</em>. Published online April 24, 2017. doi: 10.1038/s41550-017-0115.</p></div>
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<div class="field-item even"><p><a href="https://www.sciencenewsforstudents.org/article/how-solar-systems-tail-disappeared"><em>Read another version of this article at </em>Science News for Students</a></p></div>
<div class="field-item odd"><p>A. Grant. <a href="https://www.sciencenews.org/article/solar-system-has-tail">The solar system has a tail</a>. <em>Science News</em>. Vol. 184, August 24, 2013, p. 9.</p><p>R. Cowen. <a href="https://www.sciencenews.org/node/13363">Solar system’s edge surprises astronomers</a>. <em>Science News</em>. Vol. 176, November 21, 2009, p. 15.</p></div>
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<p>The solar system doesn’t have a long, twisted tail after all.</p><p>Data from the Cassini and Voyager spacecraft show that the bubble of particles surrounding the solar system <a href="http://nature.com/articles/doi:10.1038/s41550-017-0115">is spherical, not comet-shaped</a>. Observing a spherical bubble runs counter to 55 years of speculation on the shape of this solar system feature, says Tom Krimigis of the Johns Hopkins Applied Physics Laboratory in Laurel, Md. He and colleagues report the result online April 24 in <em>Nature Astronomy</em>.</p><p>“You can’t really argue with the new result,” says Merav Opher of Boston University, who was not involved in the study. “The data so loudly say that there is no tail.”</p><p>The bubble, called the heliosphere, is inflated by particles streaming from the sun and envelops all of the material in the solar system. Its shape is important because it provides clues about how the solar system interacts with interstellar space.</p><p>In the 1960s, researchers proposed that the heliosphere was either shaped like a comet or was spherical. Magnetic fields surrounding the sun and the planets look sort of like comets, with long tails extending behind them. So, scientists speculated that the heliosphere would have a tail, too. In 2013, data from the Interstellar Boundary Explorer, or IBEX, spacecraft found signs that the tail assumption was right. The probe counted the number of fast-moving atoms that are thought to be kicked inward from the edge of the solar system when they collide with charged particles from the sun. Detecting those atoms offers clues to the shape of the heliosphere, and the images suggested that solar system had a long, twisted tail that looked like a four-leaf clover (<a href="https://www.sciencenews.org/article/solar-system-has-tail"><em>SN: 8/24/13, p. 9</em></a>).</p><p>But it wasn’t clear from the data exactly how far away from the spacecraft the atoms were and therefore how far the heliosphere’s tail extended, Krimigis says. By combining more than a decade’s worth of data from the Voyager and Cassini probes, he and colleagues sought a clearer picture. The team specifically tracked how the abundance of the speedy atoms changed in different parts of the heliosphere as the intensity of charged particles streaming from the sun, the solar wind, waxed and waned. </p><p>At the front of the heliosphere, where the Voyager probes sit, when the intensity of the solar wind decreased, so did the abundance of speedy atoms. When it increased, the number went up, in lockstep. Looking at speedy atoms at the back of the heliosphere, the team saw the same changes. If there were a long tail, Krimigis says, the changes in the number of atoms wouldn’t be the same in both directions. Because the atoms would have farther to travel in a tail, it would take longer for their abundance to build up there again.</p><p>While the observational evidence now favors a spherical shape for the heliosphere, recent simulations suggest something more exotic. The bubble might actually be shaped like a croissant, Opher says. The simulations, which incorporate data from Voyager 1, show that the interaction of the magnetic fields from the sun and interstellar space squish the solar wind into two jets — what might be observed as two short tails. These jets haven’t been detected yet. But if they are, she says, they could give clues to other sets of jets seen in the universe such as those shooting from young stars or possibly even black holes.</p><span property="rnews:name schema:name" content="No long, twisted tail trails the solar system" class="rdf-meta element-hidden"></span>Mon, 24 Apr 2017 14:07:21 +0000Cassie193166 at https://www.sciencenews.org